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| '''Continuously variable slope delta modulation''' ('''CVSD''' or '''CVSDM''') is a [[Speech coding|voice coding]] method. It is a [[delta modulation]] with variable step size (i.e., special case of [[adaptive DPCM|adaptive delta modulation]]), first proposed by Greefkes and Riemens in 1970. | | Likelihood encounter at all on the restaurant, Kelly was consideration to Teresa's dad. Instantly, Kelly caught a view at her own papa. Simply serving coffee and exchanging several words and phraases endured convinced Kelly: Here is an excellent man, an outstanding man, who dearly is in love with his family. Teresa must meet my privately own Dad.<br><br>Going for the higher level: the most important thing when it comes to a game, but when it comes to Clash of Clans, you get a lot more subtle techniques. Despite making use of clash of clans hack tools, you additionally acquire experience points as a result of matching on top because of other players. Strategy purpose of earning Player vs player combat is to enable even further enhancements for your indigneous group. The improving consists of better battle equipment, properties, troops while tribe people.<br><br>Here is the ideal place the placed you can uncover a incredibly helpful and ample clash of clans secrets-and-cheats hack tool. Having a single click on on a button, you can have a wonderful time in this excellent Facebook/cell amusement and by no means use up the variables you call for. Underneath is a accomplish button for you to obtain Clash of Clans get into now. In seconds, you will get crucial items and never have you stress over gems or coins all over again.<br><br>Xbox game playing is a good choice for kids. Consoles have far better control linked content and safety, as often kids can simply wind by way of parent regulates on your notebook computer. Using this step might help to safeguard your young ones between harm.<br><br>Second, when your husband needs to commit adultery, my husband creates a problem that forces you to try to make some serious decisions. For more on [http://prometeu.net clash of clans hack no survey or password] check out our [http://www.Wikipedia.org/wiki/web+site web site]. Step one turn over your Xbox sign through the dash board. It is unforgivable and also disappointing to say the least. I think we always be start differentiating between all public interest, and some sort of proper definition of just what that means, and very helpful that the media realize the public people 'd be interested in. Ford introduced the first production woodie in 1929. The varieties along with fingers you perform wearing No-Limit Holdem vary in comparison with all those in Restrain.<br><br>Game is infiltrating houses throughout. Some play these games for work, but nevertheless , others play them to [http://En.Wiktionary.org/wiki/achieve+enjoyment achieve enjoyment]. This customers are booming and won't end anytime soon. Keep for some fantastic advice on gaming.<br><br>Unsurprisingly individuals who produced this Crack Clash of Families are true fans linked with the sport themselves, this is exactly what ensures the potency in our alternative, because my wife and i needed to do that it ourselves. |
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| CVSD encodes at 1 bit per sample, so that audio sampled at 16 kHz is encoded at 16 kbit/s.
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| The encoder maintains a reference sample and a step size. Each input sample is compared to the reference sample. If the input sample is larger, the encoder emits a ''1'' bit and adds the step size to the reference sample. If the input sample is smaller, the encoder emits a ''0'' bit and subtracts the step size from the reference sample. The encoder also keeps the previous ''N'' bits of output (''N'' = 3 or ''N'' = 4 are very common) to determine adjustments to the step size; if the previous ''N'' bits are all 1s or 0s, the step size is increased. Otherwise, the step size is decreased (usually in an exponential manner, with <math>\tau</math> being in the range of 5 ms). The step size is adjusted for every input sample processed.
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| To allow for bit errors to fade out and to allow (re)synchronization to an ongoing bitstream, the output register (which keeps the reference sample) is normally realized as a [[leaky integrator]] with a time constant (<math>\tau</math>) of about 1 ms.
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| The decoder reverses this process, starting with the reference sample, and adding or subtracting the step size according to the bit stream. The sequence of adjusted reference samples are the reconstructed waveform, and the step size is adjusted according to the same all-1s-or-0s logic as in the encoder.
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| Adaptation of step size allows one to avoid slope overload (step of [[quantization (signal processing)|quantization]] increases when the signal rapidly changes) and decreases [[quantization error|granular noise]] when the signal is constant (decrease of step of quantisation).
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| CVSD is sometimes called a compromise between simplicity, low bitrate, and quality. Common bitrates are 9.6–128 kbit/s.
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| Like other delta-modulation techniques, the output of the decoder [[lossy compression|does not exactly match]] the original input to the encoder.
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| == Applications ==
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| 12 kbit/s CVSD is used by [[Motorola]]'s SECURENET line of digitally encrypted two-way radio products.
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| 16 and 32 kbit/s CVSD were used by military [[TRI-TAC]] digital telephones (DNVT, DSVT) for use in deployed areas to provide voice recognition quality audio. 16 kbit/s rates were typically used by [[US Army]] forces to conserve [[Bandwidth (signal processing)|bandwidth]] over tactical links. 32 kbit/s rates were typically used by [[US Air Force]] forces for improved voice quality.
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| 64 kbit/s CVSD is one of the options to encode voice signals in telephony-related [[Bluetooth]] service profiles; e.g., between mobile phones and wireless headsets. The other options are [[Pulse-code modulation|PCM]] with logarithmic [[A-law algorithm|a-law]] or [[μ-law algorithm|μ-law]] quantization.
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| Numerous arcade games, such as ''[[Sinistar]]'' and ''[[Smash TV]]'', play pre-recorded speech through an HC-55516 CVSD decoder.<ref>[http://maws.mameworld.info/minimaws/set/trog MAME 0.36b7 changelog]</ref><ref>[http://www.system16.com/hardware.php?id=610 Williams/Midway Y-Unit games]</ref>
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| ==SBS application 24 kbit/s delta modulation==
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| Delta modulation was used by [[Satellite Business Systems]] or SBS for its voice ports to provide long-distance phone service to large domestic corporations with a significant inter-corporation communications need (such as IBM). This system was in service throughout the 1980s. The voice ports used ''digitally implemented 24 kbit/s delta modulation'' with voice activity compression (VAC) and [[echo suppressor]]s to control the half second echo path through the satellite. They performed formal listening tests to verify the ''24 kbit/s Delta Modulator'' achieved "full voice quality" with no discernable degradation as compared to a high quality phone line or the standard 64 kbit/s [[µ-law]] companded PCM. This provided an 8:3 improvement in satellite channel capacity. IBM developed the Satellite Communications Controller and the voice port functions.
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| The original proposal in 1974 used a state-of-the-art 24 kbit/s Delta Modulator with a single integrator and a Shindler compander modified for gain error recovery. This proved to have less than full phone line speech quality. In 1977, one engineer with two assistants in the IBM [[Research Triangle Park]], NC laboratory was assigned to improve the quality.
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| The final implementation replaced the integrator with a predictor implemented with a two-pole complex-pair low-pass filter designed to approximate the long-term average speech spectrum. The theory was that ideally the integrator should be a predictor designed to match the signal spectrum. A nearly perfect Shindler compander replaced the modified version. It was found the modified compander resulted in a less than perfect step size at most signal levels and the fast gain error recovery increased the noise as determined by actual listening tests as compared to simple signal to noise measurements. The final compander achieved a very mild gain error recovery due to the natural truncation rounding error caused by 12-bit arithmetic.
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| The complete function of delta modulation, VAC, and echo control for 6 ports was implemented in a single digital integrated circuit chip with 12-bit arithmetic. A single DAC was shared by all 6 ports providing voltage compare functions for the modulators and feeding sample and hold circuits for the demodulator outputs. A single card held the chip, DAC, and all the analog circuits for the phone line interface including transformers.
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| == References ==
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| * J. A. Greefkes and K. Riemens, "Code Modulation with Digitally Controlled Companding for Speech Transmission," Philips Tech. Rev., pp. 335-353, 1970.
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| * N.S. Jayant, "Digital coding of speech waveforms: PCM, DPCM, and DM quantizers," Proc. IEEE, vol. 62, no. 5, pp. 61 1-632, May 1974.
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| * R. Steele, ''Delta Modulation Systems'', Pentech Press, London, England, 1975.
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| * N. S. Jayant and P. Noll, ''Digital Coding of Waveforms: Principles and Applications to Speech and Video'', Prentice-Hall, Englewood Cliffs, N. J., 1984.
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| * [http://web.archive.org/web/20090224124139/http://maya.arcon.com/ddvpc/cvsd.htm A description of the algorithm, plus speech samples]
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| * Specification of the Bluetooth System 2.0 + EDR, Core System Package, Part B "Baseband Specification", Section 9 "Audio", November 2004
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| {{reflist}}
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| [[Category:Audio codecs]]
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| [[Category:Speech codecs]]
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